Defrost system for air curtain type refrigerated display case



Oct. 1, 1968 s, c wrr ET AL 3,403,525

DEFROST SYSTEM FOR AIR CURTAIN TYPE REFRIGERATED DISPLAY CASE 5 Sheets-Sheet 1 Filed Feb. 3, 1967 IN VEN7'0/25 Sterling Beckwii/ Oct. 1, 1968 s, W T ET AL 3,403,525

DEFROST SYSTEM FOR AIR CURTAIN TYPE REFRIGERATED DISPLAY CASE Filed Feb. 3, 1967 5 Sheets-Sheet 2 Oct. 1, 1968 s, BECK 'rH ET AL 3,403,525

DEFRO SYSTE F AIR CURTAIN TYPE RIGER D DISPLAY CASE Filed Feb. 3, 1967 FIG: 5

5 Sheets-Sheet 4 Filed Feb. 3, 1967 FIG, 10

S. BECKWITH ET DEFROST SYSTEM FOR AIR CURTAIN TYPE REFRIGERATED DISPLAY CASE 5 Sheets-Sheet 5 United States Patent G DEFROST SYSTEM FOR AIR CURTAIN TYPE REFRIGERATED DISPLAY CASE Sterling Beckwith, Deerfield, Ill., and Robert E. Vogel,

Menlo Park, Calif, assignors to Dual Jet Refrigeration Co., Chicago, 111., a corporation of Illinois Filed Feb. 3, 1967, Ser. No. 613,802

17 Claims. (Cl. 6282) ABSTRACT OF THE DISCLOSURE A refrigerated enclosure including driven air streams circulating across an access opening to the enclosure. The enclosure is defrosted by passing air streams through an outlet means located at the top of the enclosure. Ambient air is drawn into the enclosure during the defrosting and the ambient air is circulated over refrigerated portions of the enclosure before being passed out through the top of the enclosure.

This invention relates to an improved system for the operation of equipment utilizing refrigerating means. The invention is particularly concerned with refrigerated constructions which utilize moving streams of air employed for purposes of creating refrigerated conditions in areas of a construction located within or adjacent to the paths of the air streams. The following description is directed to a variety of improvements particularly including im proved methods and means for defrosting and for controlling frost build-up.

In describing the instant invention, reference will be made to defrosting systems for refrigerated cabinet constructions. In such constructions, air curtains are moved across an access opening for the cabinets and the character of the curtains is important with regard to eflicient operation of the construction.

In Hagen et al. Patent No. 3,134,243 and in Simons Patent No. 2,862,369, there are described refrigerated display cabinets which are provided with access openings exposed to the atmosphere while still being capable of maintaining the contents in a refrigerated state. Loss of refrigeration from the enclosed space through the access opening is reduced in a highly effective manner in these constructions by the use of a gaseous, preferably air, curtain which is continuously advanced across the open side from one edge of the opening to the opposite edge.

The air curtain in these constructions is adapted to be formed of adjacent panels of air, with the innermost panel comprising a refrigerated cold air panel, and with one or more outer panels having temperatures approaching the ambient temperature. It has been found that it is desirable to recirculate the inner cold air panel and to provide means for circulating the adjacent guard panels, to conserve the refrigeration and to maintain the enclosed Space in a satisfactory refrigerated state.

Defrosting means can readily be associated with constructions of the type described. Obviously, the constructions could be shut down whereby ambient conditions would eventually result in defrosting of the construction. On the other hand, heaters could be employed for purposes of accelerating the defrosting operations.

Available means for defrosting constructions of the type referred to are, however, not entirely satisfactory. Long shutdown periods are completely undesirable where the constructions are employed for handling of frozen food products since it would be inconvenient to move the products during defrosting, and it is undesirable to allow the products to themselves defrost.

It is a general object of this invention to provide a ice defrosting system which includes improved means and operating methods whereby defrosting of refrigerating constructions can be efiiciently undertaken.

It is a further object of this invention to provide a defrosting system of the type described which can be rapidly carried out and which avoids long shutdown periods While also avoiding severe variations in temperature of the elements within the construction.

It is a still further object of this invention to provide a defrosting system which is ideally suitable for refrigerated cabinets of the type employing circulating air streams.

It is an additional object of this invention to provide means to be employed in conjunction with cabinets of the type described which reduce the tendency toward frost build-up Within the construction.

These and other objects of this invention will appear hereinafter and for purposes of illustration, but not of limitation, specific embodiments of this invention are shown in the accompanying drawings in which:

FIGURE 1 is a vertical sectional view of one type of refrigerated cabinet designed for the use of the defrosting system of this invention;

FIGURE 2 is a sectional view of a modified refrigerated cabinet suited for the system of this invention;

FIGURE 3 is a front elevational view of the cabinet of FIGURE 2;

FIGURE 4 is an enlarged sectional view taken about the line 44 of FIGURE 3;

FIGURE 5 is a plan view, partly cut away, taken about the line 5-5 of FIGURE 4;

FIGURES 6 through 12 comprise horizontal sectional views taken about the lines 6-6 through 1212, respectively, of FIGURE 4;

FIGURE 13 is a fragmentary, vertical, sectional view taken about the line 1313 of FIGURE 4; and

FIGURE 14 is a schematic illustration of the airflow developed during defrosting of a cabinet characterized by the features of this invention.

As noted, the instant invention will be described with reference to constructions which employ air curtains moving in side-by-side relationship across an access opening of the refrigerated cabinet construction. Such air curtains are commonly employed for the purpose of forming barriers to prevent or minimize heat transfer,

The invention will be specifically described with respect to refrigerated enclosures of the type defining an access opening in one wall whereby communication with the space within the enclosure can be accomplished. The enclosures or cabinets of this invention are provided with a plurality of nozzles arranged in side-by-side relationship across one edge of an access opening and corresponding inlets are located across the opposite edge of the access opening. The inner nozzles and inlets are provided for the passage of a refrigerated stream across the access opening while the adjacent outer nozzles and inlets circulate progressively warmer air panels. The inner refrigerated stream is circulated through a passage having refrigeration coils located therein and one or more of the outer adjacent streams may also be refrigerated.

In the course of the operation of a construction of the general type referred to, frost tends to build up on the refrigeration coils and on other surfaces contacted by the refrigerated air stream. The improvement of this invention generally relates to means for defrosting the construction by providing for the introduction of ambient air into the construction. The ambient air is drawn through passages in the construction whereby this warmer air contacts the refrigerated coils as well as other frost bearing areas. The circulation of the ambient air in the construction is undertaken in a specific manner whereby the defrosting can be rapidly carried out. The means employed for drawing the ambient air into the construction and which provide for the circulation comprise, to a large extent, the means used during the refrigeration cycle of the construc tion whereby extensive outlays for special defrosting equipment are not necessary.

The accompanying drawings illustrate refrigerated cabinet designs adapted to be employed in conjunction with the defrosting system of this invention. In FIGURE 1, there is shown a refrigerated cabinet which includes a top wall 12, a bottom wall 14, a back wall 16 and a front wall 18. The front wall 18 defines an opening 20 which provides access to the interior 22 of the refrigerated cabinet. An inner wall 24 defines the extent of the refrigerated space.

A partition 26 is formed to define an inner passage 28 and an outer passage 30 in the construction. The inner passage 28 carries a refrigerating means 32 and a circulating fan 34 provides for movement of air past the refrigerating means and through the passage 28. A similar circulating fan 36 is provided for the outer passage 30.

Inlets 38 are provided for each of the passages 28 and 30. The streams 40 and 42 which cross the access opening pass into these inlets and are driven through the passages to oulet nozzles 48. Screens may be included over the inlets 38 to prevent entry of insects or other foreign materials into the passages. Where the screens are provided, they should be associated with heating means whereby the surface temperature of the screens will be maintained a few degrees above the temperature of the air streamfl This arrangement reduces the tendency toward frost accumulation on the screens.

During the refrigeration portion of the operation cycle, air is circulated through the inner passage 28 whereby a refrigerated stream can be maintained through the action of the refrigerating means. The inner stream crossing the access opening 20 will therefore comprise a refrigerated stream. A second circulating stream passes through the passage 30 whereby a guard panel of air crosses the access opening in side-by-side relationship with respect to the refrigerated air panel.

As the refrigerating cycle progresses, frost will build up primarily in the passage 28 and particularly on the refrigerating means. When the frost has built up to the point that the operating efiiciency is decreased to an undesirable level, a defrosting portion of the cycle is commenced. In accordance with this invention, the defrosting operation is instituted by operating various elements in the construction whereby ambient air will be introduced into the con- 1 struction.

The ambient air is adapted to be drawn into the construction through the inlet 38 provided for the passage 30. As indicated by the arrows shown in FIGURE 1, the air will follow a course through the passage 30 and out through the nozzle 48 for the passage 30. At this point, the air stream diverges from the path maintained during the refrigerating cycle. As shown by the arrows, the air stream passes into the inlet 38 of the passage 28 whereby the ambient air will pass into contact with the refrigerating means. Thereafter, the ambient air is caused to progress through the passage 28 to an outlet means 50 located at the top of the cabinet.

The ambient air can be drawn into the outer passage 30 by means of the circulating fan 36. During the refrigerating cycle, the introduction of the ambient air is resisted by the outer air stream 49. Since this air stream does not pass into the passage 28 during the defrosting cycle, the introduction of ambient air is not impeded.

The ambient air will follow a path into the inner passage 30 after crossing the access opening since there is no air stream corresponding to the stream 42 during the defrosting portion of the operating cycle. The absence of the stream 42 causes the ambient air issuing from the nozzle 48 of the passage 30 to follow a natural path into the inlet for the passage 28.

The inner stream or panel 42 is eliminated during the defrosing cycle since the air in the passage 28 passes out through the outlet 50 instead of progressing to the nozzle 48 for this passage. A fan 52 can be provided in association with the outlet 50 in order to assist in drawing the ambient air out through the top of the cabinet. A baffle 54 normally located in position to close off the outlet 50 can be provided whereby air in the passage 28- will be forced to enter the outlet 50. It will be noted that the outlet 54 angles away from the normal flow of air during the refrigerating cycle. This arrangement is preferred, particularly where no baffle is employed since the angular relationship will decrease any tendency of the refrigerated air to pass out through the outlet 58.

The outlet 50 may comprise a plurality of spaced apart members extending across the passage 30. Sufiicient spacing must be provided so that the stream of air in the passag 30 can be properly circulated for passage across the access opening. Instead of stationary conduits St), collapsible elements for forming the conduit walls may be employed. These elements could normally lie against a surface of the passage 30 and when raised, they would define the conduit passage. The conduit means would then be out of position for free passage of air during the refrigerating cycle. The conduit would only be moved into position when the defrosting cycle began.

FIGURES 2 through 14 cover an alternative cabinet arrangement 61 which is ideally suited for operation in accordance with this invention. The cabinet comprises outlet nozzles 60 and 62 and inlets 64 and 66. Accordingly, the construction is adapted to provide for the movement of panels of air across an access opening in the manner of the previously described construction.

The inner, refrigerated panel of air is delivered to the nozzle 62 through passages 68 and 70 (FIGURE 8). These passages communicate with rectangular, vertically disposed passages 72 and 74 extending upwardly along the back of the construction. Substantially horizontal continuations 76, 78 (FIGURE 11) are provided for the passages 72 and 74. The refrigerated air panel moving across the access opening enters the inlet 66 for entry into the passages 76 and 78.

A similar arrangement is provided for the guard panel issuing from the nozzle 60 and entering the inlet 64. Substantially horizontal passages 84 and 86 (FIGURE 12) collect the incoming air. The passages 84 and 86 communicate with vertical passages 92 and 94, and these passages in turn communicate with upper passages 96 and 98 (FIGURE 7).

As best shown in FIGURE 4, a third duct 88 is located at the top of the cabinet. A circulating fan 89 draws air into this duct for passage out through nozzle 90. With this arrangement, a stream of ambient air is forced downwardly adjacent the guard panel of air issuing from the nozzle 60. This additional panel of air tends to reduce turbulence as the air panels move across the access open ing of the cabinet. Specifically, the additional panel will tend to prevent spilling of any air from the guard panel beyond the inlet 64. This, of course, serves to avoid any spilling of air from the refrigerated panel. The additional panel of ambient air is directed whereby the majority of the air will spill outside the cabinet.

Refrigerating coils 97 can be located within the passages 76 and 7S. Circulating fans 99 are located within the vertical passages 72, '74, 92, 94 (FIGURE 10). It will be apparent, however, that other locations may be provided for these elements. Access to the fans for maintenance purposes is simplified in the illustrated arrangement by providing removable plates 101 for access to the fans from the interior of the cabinet.

Circulation of the respective air streams provides for highly efficient maintenance of refrigeration in the cabinet construction. The construction disclosed is also uniquely suitable for operation in accordance with the concepts of this invention since circulation of air streams for defrosting purposes can be very easily undertaken.

To accomplish defrosting in accordance with this invention, a door 100 is located at the top of each of the passages 72 and 74. When pivoted to the position shown in FIGURE 14, the respective passages 72 and 74 communicate with the outside atmosphere through outlet conduits 102.

The circulation of air in the construction during the defrosting cycle proceeds in a manner similar to the circulation referred to with respect to FIGURE 1. Specifically, ambient air is drawn into the inlet 64 and is circulated through the passages 84, 86, 92, 94 and 96, 98. The air passes out of the nozzle 60 and then into the inlet 66. The air then passes up through the passages 72 and 74 and into the atmosphere through the outlet conduits 102. Fans can be associated with the conduits 102 to assist in drawing the air out of the construction; however, the natural flow of air through these conduits will be satisfactory.

The circulation of ambient air in the manner of this invention takes place in an extremely efficient manner with the construction illustrated in FIGURES 2 through 14. This type of construction is particularly suitable for operation in accordance with this invention since the pro vision of the outlets 102 is greatly simplified wherein vertical passages are situated in side-by-side relationship across the rear of the construction in the manner shown.

As indicated, the system of this invention is extremely efficient from the standpoint of providing for rapid defrosting without the necessity for complicated or expensive auxiliary equipment. The ambient air which passes over the refrigerator coils and over the circulating fans has a low dew point and this is drier air than is the ambient air taken into the front of the cabinet. Thus, all of the frost on the coil and some of the moisture in the ambient air is carried off in the water drain. The location of the outlet or outlets for the ambient air at the top of the construction provides distinct advantages. Thus, the ambient air is cooled considerably during defrosting, and it would be undesirable to have this air spilling out at a lower level since it could cause discomfort to individuals in the vicinity of the enclosure. The natural inertia of the air makes it quite simple to provide for discharge at this point. Furthermore, the upward discharge can assist in providing desirable air circulation in the location of the construction as well as providing uniformity in temperature distribution.

Various means can be employed for initiating the defrosting portion of the operating cycle. Timers can be employed for operating a motor connected to the door 100 whereby opening and closing of the door can take place at predetermined intervals. Obviously, auxiliary fans which assist in circulating the air and drawing the air out of the top of the cabinet can also be operated by the timer.

Sensing means can also be employed whereby the defrosting operation -will take place when certain conditions such as temperature or air velocity reach predetermined values. Obviously, dampers or baffie plates which provide communication between the refrigerated air passage and the outside atmosphere at the initiation of the defrosting cycle can be operated in tandem by valves or other means responding to the sensing devices.

Light insulation material such as Styrofoam can readily be utilized in the cabinet design of FIGURES 2-14. Such material, however, tends to heat up slowly and any frost collecting on the surfaces will therefore be more difiicult to remove. Accordingly, the instant invention contemplates the provision of thin sheets of material which will conduct heat at a high rate. The ambient air will, therefore, remove frost from such surfaces in a more efiicient manner. Sheets of aluminum foil serving as linings for the passage walls are suitably employed for this purpose.

The construction of the substantially horizontal passages 68, 70, 76, 78, 84, 86 and 96, 98 is similar in many respects. Referring to the bottom of the cabinet, it will be noted that the passages 84 and 86 are located at a lower level than the passages 76, 78. All of these passages are tapered whereby a relatively long, narrow mouth portion is presented to the inlets 64 and 66. The taper is such that relatively short but wide openings are provided at the opposite ends of the passages for communication with the vertically disposed passages. As shown in FIGURE 11, the lower passages 84 and 86 taper toward the exterior pair of vertical passages 94 and 92. The passages 76 and 78 communicate with vertical passages 72 and 74. It will be noted that in the design illustrated, the refrigerated streams are maintained away from the exterior walls to provide minimum heat loss.

In the case of the passages 76 and 78, a relatively large interior cross section is desirable. This permits location of suitable refrigerating coils within these pass-ages.

The upper horizontal passages 68. 70, 96 and 98 are designed along the same lines as the lower horizontal passages. In accordance with the preferred form of the invention, however, specific dimensional limitations are applied in the formation of these upper passages. As shown in FIGURE 4, a taper is provided from the outlet nozzles to the point of communication with the vertical passages.

When comparing FIGURE 4 with FIGURES 7 and 8, it will be noted that in horizontal section, the air stream moves from a small dimension to a large dimension while in vertical section, the opposite is true. By properly controlling the taper, the upper passages can be designed whereby the cross-sectional area at any given point in the passages will be substantially the same as the area at any other point. For example, the passages 72 and 74 may have dimensions four inches by nine inches for a crosssectional area of 36 inches. The entry end of the passage 68 will have this same dimension; however, the four inch dimension will taper downwardly to a one and one-half inch dimension at the end of the passage 68. The nine inch dimension on the other hand will increase to 24 inches adjacent the outlet nozzle whereby a cross-sectiorral area of 36 inches is maintained.

By controlling the cross-sectional area within the passages, a minimum amount of disturbance of the air streams will be realized. There will be no significant disruption as might occur where different cross-sectional areas would cause change in air pressure and change in speeds.

The refrigerated cabinet construction is preferably designed as shown in FIGURES 2 and 3. This construction includes a U-shaped rigid frame member which may be formed of bar stock but which preferably comprises a channel cross section. Legs 112 and 114 extend downwardly from the bottom portion of the structural member 110. A foot plate 116 is associated with each leg whereby the structural members can be secured to a supporting base 117.

A structural member is preferably located on either side of the cabinet. The foam members which make up the passages are adapted to be attached to the structural members whereby all of the load will be borne by the structural members Without any load being carried by the foam.

The structural members are preferably provided with perforations 118 whereby shelf brackets 120 of a conventional design can be readily attached to the structural members. The weight of items placed on the shelves 122 will also be borne entirely by the structural members 110 and the supporting legs. When considering FIGURES 2 and 3, it will be obvious that any number of cabinet sections could be located in side-by-side relationship whereby side walls need only be employed With respect to the outermost sections.

The structural arrangements illustrated in FIGURES 2 and 3 also provide an extremely simple means for including interior and exterior coverings. A sheet 124 of metal having a cross section corresponding to the U-shape of the members 110 can be easily attached to these members. If desired, this sheet may overlap the perforations 118 of the member 110 whereby corresponding perforations can be provided in the sheet for exposing the perforations 118. Openings may also be provided in the sheet in the area of the plates 101.

A similar sheet of metal can obviously be attached around the exterior of the foam members forming the passages. Such a covering will have no significant weight whereby there will be no danger of collapsing the passages formed by the foam members.

Various means can be associated with the cabinet construction to provide improved conditions for resisting the build-up of frost. In FIGURE 1, there is illustrated a night cover 126 which is dimensioned to correspond with the access opening 20. This cover will serve as a means for preserving cold within the cabinet during times when sales are not being made. Obviously, the cover can be put in place each night by a store operator, and at this time, the operator may adjust the refrigeration system. If desired, a suitable switch may be automatically operated through engagement with the night cover when it is put in place whereby the desired change in the refrigerating operation can take place automatically.

In the operation of a cabinet utilizing a night cover 125, the compressor running time will be substantially reduced since there will be considerably less cold loss when the cover is in place. In this connection, the cover is preferably formed from a panel of insulation material.

Variations in the refrigeration cycle can also be undertaken with the cover in place. Specifically, the structure may operate to substantially reduce the cabinet temperature, for example from a normal operating temperature of -l to 30 F. In the case of ice cream, for example, the product will become very hard with the cover in place which is extremely desirable for purposes of maintaining quality. Such lower temperatures cannot be utilized, particularly where humidity is relatively high, because of rapid frost build-up. With the night cover in place, however, such frost build-up does not occur.

FIGURE 4 illustrates a further variation in the cabinet construction wherein a heater 128, for example a rod-type resistance heater, is located in the passage for the guard stream. In the illustrated arrangement, the heater is positioned adjacent the outlet nozzle 60; however, this heater could be provided in other locations for contact with the guard stream.

The heater is operated whereby the temperature of the air in the guard stream will be from about 2 to 10 higher and preferably 5 to 7 F. higher than the temperature would be without the presence of the heater. It will be appreciated in this connection that the guard stream temperature will be substantially below ambient, for example in the area of 40 F., due to its proximity to the refrigerated stream and due to spilling of portions of the refrigerated stream into the guard stream.

The provision of the heater provides remarkable results from the standpoint of controlling moisture build-up in the construction. Without the heater, moisture will begin collecting in the guard duct, particularly in the honeycomb outlet nozzle, at relative humidity of about 60 percent. By providing the heater and by controlling the temperature in the manner described, moisture build-up can be avoided up to relative humidity as high as 78 percent. This is extremely advantageous, particularly where the cabinets are employed in locations without air conditioning. Since the humidity is likely to be higher in such areas, any means which will reduce moisture build-up in the construction is of considerable importance.

It will be understood that various changes and modifications may be made in the system described which provide the characteristics of this invention without departing from the spirit thereof particularly as defined in the following claims.

That which is claimed is:

1. In a construction comprising a refrigerated enclosure including refrigerating means, circulating means for driving air into contact with said refrigerating means and passage means for directing the refrigerated air whereby the interior of said enclosure is adapted to be cooled, said enclosure defining an opening for access to the interior of the construction, at least two air inlet means and corresponding outlet nozzles extending in side-by-side relationship across opposite edges of said opening, said passage means including separate passages communicating the respective nozzles and inlets, said circulating means operating to drive separate air streams through said passages and across said access opening, and said refrigerating means being located in one of said passage means for refrigerating the innermost stream crossing said access opening, the improvement comprising means for defrosting said enclosure comprising an outlet communicating with said one passage means, means for opening said outlet, said circulating means operating during defrosting to draw ambient air into the other passage means, said ambient air passing through said other passage means, across said opening and into said one passage means, said ambient air in said one passage means contacting elements of said enclosure including said refrigerating means, and mean for passing said ambient air out of said enclosure through said outlet after said contact with said elements, said outlet means being located at the top of said cabinet, and wherein said ambient air moves upwardly for passage out of said cabinet as a result of the normal movement imparted to the air by said circulating means.

2. A construction in accordance with claim 1 wherein said passage means include a plurality of vertically disposed passages located in side-by-side relationship across the rear of the construction.

3. A construction in accordance with claim 2 wherein two of said passages carry refrigerated air, and including outlet means communicating exclusively with said two passages.

4. A construction in accordance with claim 1 including additional circulating means adjacent said outlet operating to assist in withdrawing the ambient air from said enclosure.

5. A construction in accordance with claim 1 including damper means adapted to open communication with said outlet and to close communication between the passage carrying the refrigerated stream and the outlet nozzle for the refrigerated stream passage.

6. A construction in accordance with claim 1 wherein said passages are lines with thin sheets of material having high heat conductivity.

7. A construction in accordance with claim 1 wherein said passage means include a first set of substantially horizontally disposed sections for receiving air from said inlet means, substantially vertically disposed sections communicating with said horizontally disposed sections, and a second set of substantially horizontally disposed sections for passing air from the vertical sections to said nozzles.

8. In a method for defrosting of a refrigerated enclosure which defines an open side for access to the interior of the construction, at least two air inlet means and corresponding inlet nozzles extending in side-by-side relationship across opposite edges of said open side, refrigerating means, circulating means for driving air into contact with said refrigerating means, and passage means for directing the refrigerated air whereby the interior of the enclosure is adapted to be cooled, said passage means including separate passages communicating the respective nozzles and inlets, said circulating means operating to drive separate air streams through said passages and across said access opening, and said refrigerating means being located for refrigerating the innermost stream crossing said access opening, and including a door at the top of the enclosure and means for opening said door for exposing the passage carrying said innermost stream to the atmosphere, the improvement in a method for defrosting said enclosure comprising the steps of drawing ambient air into the enclosure through the inlet means for the passage adjacent the passage holding said refrigerating means, circulating said ambient air through said adjacent passage and out through the outlet nozzle for said adjacent passage for movement across said access opening, said ambient air then moving into the inlet means for said passage holding the refrigerating means, circulating the ambient air through said last mentioned passage for contact with the refrigerating means and with the walls of said last mentioned passage, and passing said ambient air from said last mentioned passage out through the top of the refrigerated enclosure.

9. A method in accordance with claim 8 wherein the refrigerated enclosure includes at least two separate passages holding refrigerating means for purposes of forming the refrigerated air stream moving across said access opening, and wherein said ambient air is circulated through each of said last mentioned passages.

10. A method in accordance with claim 8 including the step of closing off communication with the outlet nozzle for the passage holding the refrigerating means during defrosting.

11. In a construction comprising a refrigerated enclosure including refrigerating means, circulating means for driving air into contact with said refrigerating means and passage means for directing the refrigerated air whereby the interior of said enclosure is adapted to be cooled, said enclosure defines an opening for access to the interior of the construction, at least two air inlet means and corresponding outlet nozzles extending in side-by-side relationship across opposite edges of said opening, said passage means including separate passages communicating the respective nozzles and inlets, said circulating means operating to drive separate air streams through said passages and across said access opening, and said refrigerating means being located for refrigerating the innermost stream crossing said access opening, and wherein said ambient air is passed through the passage carrying the refrigerated air stream during defrosting, the improvement wherein said passage means include a first set of substantially horizontally disposed sections for receiving air from said inlet means, substantially vertically disposed sections communicating with said horizontally disposed sections, and a second set of substantially horizontally disposed sections for passing air from the vertical sections to said nozzles, and wherein each -set of horizontally disposed sections comprise upper and lower conduit means, at least said upper conduit means having a tapered shape With one end adjacent said nozzles defining a relatively long and narrow mouth substantially coextensive with said nozzles, and with the other end adjacent said vertically disposed sections defining a relatively short and wide mouth for connection with said vertical sections, and including means for defrosting said enclosure comprising an outlet communicating with said passage means, means for opening said outlet, means for drawing ambient air into said passage means for contact with elements of said enclosure including said refrigerating means, and means for passing said ambient air out of said enclosure through said outlet after said contact with said elements, said outlet means being located at the top of said cabinet, and wherein said ambient air moves upwardly for passage out of said cabinet as a result of the normal movement imparted to the air by said circulating means.

12. A construction in accordance with claim 11 wherein said vertical sections include at least two interior conduits disposed in side-by-side relationship, and at least two exterior conduits on opposite sides of said interior conduits, and wherein said horizontally disposed sections comprise pairs of conduit means communicating with said interior conduits and separate pairs of conduit means communicating with said exterior conduits. I

13. A construction in accordance with claim 11 wherein the cross-sectional area of the interior passage defined by the tapered conduit means is substantially the same at different points along the length of the tapered conduit means.

14. In a construction comprising a refrigerated enclosure including refrigerating means, circulating means for driving air into contact with said refrigerating means and passage means for directing the refrigerated air whereby the interior of said enclosure is adapted to be cooled, said enclosure defining an opening for access to the interior of the construction, at least two air inlet means and corresponding outlet nozzles extending in side-by-side relationship across opposite edges of said opening, said passage means including separate passages communicating the repective nozzles and inlets, said circulating means operating to drive separate air streams through said passages and across said access opening, and said refrigerating means being located for refrigerating the innermost stream crossing said access opening, the improvement comprising U-shaped structural members for supporting the walls and passage means of said enclosure, said U- shaped members comprising upper and lower, substantially horizontally disposed legs, and an intermediate substantially vertically disposed section, said legs and said intermediate section defining the interior configuration 0f the enclosure, and including means for defrosting said enclosure comprising an outlet communicating with said passage means, means for opening said outlet, means for drawing ambient air into said passage means for contact with elements of said enclosure including said refrigerating means, and means for passing said ambient air out of said enclosure through said outlet after said contact with said elements, said outlet means being located at the top of said cabinet, and wherein said ambient air moves upwardly for passage out of said cabinet as a result of the normal movement imparted to the air by said circulating means.

15. A construction in accordance with claim 14 including bracket connecting means defined by said intermediate sections, bracket means attached to said connecting means and shelves supported by said bracket means whereby all of the weight of goods included within the enclosure is transmitted to said structural members.

16. A construction in accordance with claim 14 wherein said structural members are located at least at either end of said enclosure, and including an inner liner attached to said structural members and extending across the enclosure for defining the inner walls of the enclosure.

17. A construction in accordance with claim 14 including vertically disposed legs secured to said structural members and extending downwardly to a support for said enclosure whereby all of the load carried by the structural members is transmitted to said vertical legs.

References Cited UNITED STATES PATENTS 3,094,851 6/ 1963 Beckwith 62256 3,128,609 4/1964 Beckwith et al. 62256 3,186,185 6/1965 Bently et al. 62255 3,226,945 1/ 1966 Spencer 62256 3,304,736 2/1967 Brennan et al. 62176 ROBERT A. OLEARY, Primary Examiner.

W. E. WAYNER, Assistant Examiner. 

